Drafting instrument.



J. LARSON.

DRAFTING INSTRUMENT. APPLICATION FILED DEC-12,1918.

1,299,964. Patented Apr. 8,1919.

JULIUS ARSON, 'or NEw HAVEN, conivnorrcur, ASSIGNQR or, oivn riiitr TO moron SWANSON, or new HAVEN,"CONNEGTICUT.

Specification of Letters Patent.

Patented Apr. 8, 1919.

Application filed December 12, 1918. Serial No. 266,417.

To all whom it may concern Be it known that I, JULIUS LARSON, a subject of the King of Sweden, residing at New Haven, in the county of New Haven and State of Connecticut, have invented a new and useful Improvement in Drafting Instruments; and I do hereby declare the following, when taken in connection with the accompanying drawings and the characters of reference marked thereon, to be a full, clear, and exact description of the same, and which said drawings constitute part of this application, and represent, in-

Figure 1 a side view of a drafting instrument constructed in accordance with my invention.

Fig. 2 an underside view of the same.

Fig. 3 a broken sectional view showing the connection between the ends of the legs and the blocks.

This invention relates to an improvement in drafting instruments and particularly to a device used in drawing semi-ovals, the object of the invention being to provide an adjustable device with which ovals or semi ovals of various major and minor axes may be perfectly transcribed; and the invention consists in the construction hereinafter de scribed and particularly recited in the claims.

In carrying out my invention I employ two legs 5 and 6 hinged together at their upper ends in the manner of a draftsmans compass. Beyond the pivot point 7 the legs are connected by a ring-like spring the tendency of which is to expand the outer ends of the legs which are adapted to be drawn together by means of a nut 9 threaded upon a screw stem" 10 which passes through a stop eye 11 on one of the legs as 6 and is pivotally connected with the other leg. The ends of the legs 5 and 6 are respectively pivoted to blocks 12 and 13. Mounted in the block 13 is a horizontal guide bar 14 which extends through a clearance hole formed for it in the block 12 which is free to ride back and forth upon the guide-bar 14:. Rigidly secured to the block 12 by a screw 15 is a band 16 of flexible spring metal, the other end 17 of which passes between the outer wall of the block 13 and a block 12 by the screw 15, this finger bearing against the inner face of the band 16 and a similar spring finger 21 will be secured to the outer face of the block 13 and so as to expandagainst the inner face of the adjustable end of'the band, the tendency of these spring fingers being to force the band outward. Preferably and as herein shown pins 22 and 23 will be secured to the blocks 12 and 13, and so that their points project slightly below the lower faces of the blocks to locate the blocks on a sheet of drawing paper or the material on which the oval is to be made. To draw a semi-oval, the legs 5 and 6 will be adjustedaccording to the major axis of the oval. The band 16 will then be adjusted according to the minor axis of the oval, and when adjusted, will be clamped to the block 13 by the screw 19. The outer edge of band thus forms half of an oval and the band forms a surface against whichapencil may rest in scribing the semi-oval. The devicev is then reversed in position, the points of the pins 22 and 23,

being inserted inthe holes previously formed by them, and the other side of the oval may a band rigidly secured to one of the blocks and adjustably securedto the otherblock,

and spring fingers bearing against the inner faces of the band at opposite ends.

3 2. A drafting instrument comprising a pair of legs hinged together, a spring con nected with the said legs and tending to separate the ends of the same, means for drawing the legs together a block pivotally connected With each leg, a rod fixed to one block specification in the presence of two subscriband extending through the other block, pins ing Witnesses. securedto said' blocks and projecting. below" the lower faces thereof, and at flexible band JULIUS LARSON fixed to one block and adjustably connected Witnesses: with the other block; JOHN-1* SVEN-SSON,

In testimony whereof} Iha ve'si'gned" this GORNELIA SVI ENSGN.

copies of this patent may be obtaineddor -nve cents each -by-addressing the Commissioner of Patents,

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